feat(page): add page.isClosed method (#2588)

Fixes #2501.

docs/api.md

@@ -97,6 +97,7 @@
   * [page.goForward(options)](#pagegoforwardoptions)
   * [page.goto(url, options)](#pagegotourl-options)
   * [page.hover(selector)](#pagehoverselector)
+  * [page.isClosed()](#pageisclosed)
   * [page.keyboard](#pagekeyboard)
   * [page.mainFrame()](#pagemainframe)
   * [page.metrics()](#pagemetrics)
@@ -1180,6 +1181,12 @@ If there's no element matching `selector`, the method throws an error.
 
 Shortcut for [page.mainFrame().hover(selector)](#framehoverselector).
 
+#### page.isClosed()
+
+- returns: boolean
+
+Indicates that the page has been closed.
+
 #### page.keyboard
 
 - returns: <[Keyboard]>

lib/Page.js

@@ -72,6 +72,7 @@ class Page extends EventEmitter {
    */
   constructor(client, target, frameTree, ignoreHTTPSErrors, screenshotTaskQueue) {
     super();
+    this._closed = false;
     this._client = client;
     this._target = target;
     this._keyboard = new Keyboard(client);
@@ -131,7 +132,10 @@ class Page extends EventEmitter {
     client.on('Inspector.targetCrashed', event => this._onTargetCrashed());
     client.on('Performance.metrics', event => this._emitMetrics(event));
     client.on('Log.entryAdded', event => this._onLogEntryAdded(this._client, event));
-    this._target._isClosedPromise.then(() => this.emit(Page.Events.Close));
+    this._target._isClosedPromise.then(() => {
+      this.emit(Page.Events.Close);
+      this._closed = true;
+    });
   }
 
   /**
@@ -876,6 +880,13 @@ class Page extends EventEmitter {
     }
   }
 
+  /**
+   * @return {boolean}
+   */
+  isClosed() {
+    return this._closed;
+  }
+
   /**
    * @return {!Mouse}
    */

test/page.spec.js

@@ -54,6 +54,12 @@ module.exports.addTests = function({testRunner, expect, puppeteer, DeviceDescrip
       dialog.accept();
       await waitEvent(newPage, 'close');
     });
+    it('should set the page close state', async({ browser }) => {
+      const newPage = await browser.newPage();
+      expect(newPage.isClosed()).toBe(false);
+      await newPage.close();
+      expect(newPage.isClosed()).toBe(true);
+    });
   });
 
   describe('Page.Events.error', function() {